如何从命令行执行java .class [英] How to execute a java .class from the command line

问题描述

我有一个已编译的java类：

I have a compiled java class:

Echo.class

public class Echo {
    public static void main (String arg) {

            System.out.println(arg);
    }
}

我 cd 到目录并输入： java Echohello

我收到此错误：

C:\Documents and Settings\joe\My Documents\projects\Misc\bin>java Echo "hello"
Exception in thread "main" java.lang.NoClassDefFoundError: Echo
Caused by: java.lang.ClassNotFoundException: Echo
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: Echo.  Program will exit.

在我可以从命令行运行的表单中获取我的java代码的最简单方法是什么因为不得不使用Eclipse IDE？

What is the simplest way to get my java code in a form that I can run from the command line as apposed to having to use Eclipse IDE?

推荐答案

尝试：

java -cp . Echo "hello"

---

假设您编译时使用：

---

Assuming that you compiled with:

javac Echo.java 

那么当前目录可能不在你的类路径中（java查找.class定义）

Then there is a chance that the "current" directory is not in your classpath ( where java looks for .class definitions )

如果那是案例和列出您的目录显示的内容：

If that's the case and listing the contents of your dir displays:

Echo.java
Echo.class

然后任何一个可能有效：

Then any of this may work:

java -cp . Echo "hello"

或

SET CLASSPATH=%CLASSPATH;.  

java Echo "hello"

后来为弗雷德里克指出你会收到另一个错误消息就像。

And later as Fredrik points out you'll get another error message like.

线程main中的异常java.lang.NoSuchMethodError：main

当发生这种情况时，去看看他的答案:)

When that happens, go and read his answer :)

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